After a dance composing sad songs (7)
I believe the answer is:
ballads
'songs' is the definition.
(ballad is a kind of song)
'after a dance composing sad' is the wordplay.
'after' says to put letters next to each other.
'a dance' becomes 'ball' (ball is a kind of dance).
'composing' indicates anagramming the letters.
'sad' is an anagram of 'ads'.
'ball' next to 'ads' is 'BALLADS'.
(Other definitions for ballads that I've seen before include "Popular songs" , "Soppy songs!" .)